Retinal Nerve Fiber Layer Thickness Measurements via SD-OCT in
Pediatric Patients
Ihsan Yilmaz1, Abdullah Ozkaya1, Gonul Karatas1, Ahmet Taylan Yazici1
1
Beyoglu Eye Training and Research Hospital, Istanbul
Corresponding Author: Ihsan Yilmaz, MD
Address: Bereketzade Cami Sokak No:2
Beyoglu / Istanbul TURKEY
Phone: +90 532 3455972
E-mail: ihsanyilmaz.dr@gmail.com
1
Abstract:
Purpose: To determine the normative values of the retinal nerve fiber layer thickness
(RNFL) via spectral-domain optical coherence tomography (SD-OCT) in healthy
pediatrics.
Methods: Sixty eyes of 30 healthy pediatric patients (20 females, 10 males) were
included in this prospective study. After full ophthalmologic examination RNFL
measurements were performed via Spectralis SD-OCT.
Results: The mean age was 10.8 ± 3.1 years (range 6 - 15). The mean central macular
thickness was 261 ± 27 μm (range 223 - 434). The mean RNFL thickness was 127.9 ±
13.1 μm (range 109 – 160 μm) for superior quadrant; 76.7 ± 11.9 μm (range 15 – 93
μm) for temporal quadrant; 130.1 ± 10.5 μm (range 98 – 149 μm) for inferior quadrant
and 84.5 ± 11.7 μm (range 59 – 107 μm) for nasal quadrant. The mean average RNFL
thickness was 104.9 ± 6.7 μm (range 90 – 116 μm).
Conclusion: The means and normative reference ranges of RNFL thickness are
provided for Spectralis OCT in healthy pediatrics, between 6-15 years old, and this
values can be used as a standard to compare those of children suspected of having
retinal or optic nerve abnormalities.
Keywords: retinal nerve fiber layer thickness, RNFL, optical coherence tomography,
OCT, normative data
INTRODUCTION:
Optical coherence tomography (OCT) is a noninvasive, cross-sectional and
reproducible imaging technique that can measure retinal nerve fiber layer thickness
(RNFL) quantitatively.1 OCT has become a popular technique for diagnosing and
determining progression of glaucoma.2 RNFL can evaluate with slit-lamp
biomicroscopic examination. However, automated computerized devices can measure
the RNFL quantitatively and objectively.3 Beside of being a diagnostic tool, OCT also
can be used for monitoring disease progression and the effectiveness of treatment.
The first description of OCT by Huang et al was in 1991.4 OCT works similar
way with ultrasound but it uses light waves instead of sound waves.5 For measuring the
light echoes, OCT uses a spectrometer.5 Historically, the first systems were timedomain (TD-OCT) technologies. With recent advances in OCT technologies, spectraldomain (SD-OCT) is became available.6 Because of SD-OCT has the advantage of
improved image quality and resolution, smaller morphologic changes became
identifiable.7
Retinal nerve fiber layer thickness may affect from many ocular and systemic
disease. Physicians need normal databases to distinguish normal and abnormal RNFL
measurements. Previous studies have proved the feasibility of OCT in the pediatric
population.8,9 However all OCT devices have an integrated normative database only for
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adult subjects. Some earlier studies have reported normative values in children for time
domain OCT devices10-12; similar reports using spectral domain OCT devices are much
less available. This study, we used Spectralis SD-OCT (Heidelberg Engineering, Inc.,
Vista, CA) and we aim to present RNFL measurements in healthy pediatric subjects.
MATERIALS and METHODS:
Sixty eyes of 30 patients (20 female, 10 male) were included in this prospective
cross-sectional study. The inclusion criteria were: age 6 to 15 years old, best-corrected
visual acuity 20/20 or better, refractive error not exceeding ±3 diopters spherical
equivalent, no ophthalmic or systemic disease, no prior ocular surgery, no medical or
family history of retinal diseases or glaucoma. Parents of all participants were
volunteers and the study was performed according to the Helsinki declaration. This
study was approved by the local ethics committee.
All subjects underwent a full ophthalmic examination, including SD-OCT
examination. SD-OCT scanning was performed using Spectralis. This OCT system has
a resolution of 7 µm and the light source used is SLD centered at a wavelength of 870
nm. Device has eye-tracking technology recognizes the presence of eye movement then
repositions the scan pattern and discards scans with motion artifacts. Also high speed
scanning eliminates chances of artifacts.
RNFL thickness measured with 16 averaged consecutive circular B-scans
(diameter of 3.5 mm) via Spectralis OCT. The device has an online tracking system to
compensate for eye movement. The RNFL thickness was automatically segmented
using the Spectralis software ver. 4.0.0.0).13
The results between genders compared with independent samples t test and
p<0.05 was considered statistically significant. SPSS 20 (SPSS Inc., Chicago, IL, USA)
software was used.
RESULTS:
The mean age was 10.8 ± 3.1 years (range 6 – 15 years). The mean refractive
error was 0.22 ± 1.75 diopter spherical equivalents. The mean RNFL thickness was
127.9 ± 13.1 μm (range 109 – 160 μm) for superior quadrant; 76.7 ± 11.9 μm (range 15
– 93 μm) for temporal quadrant; 130.1 ± 10.5 μm (range 98 – 149 μm) for inferior
quadrant and 84.5 ± 11.7 μm (range 59 – 107 μm) for nasal quadrant. The mean average
RNFL thickness was 104.9 ± 6.7 μm (range 90 – 116 μm) (Table1).
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Table1. The RNFL thickness measurements (μm) in pediatrics.
Female
Male
Total
S
127.9 ± 13.2
(109-160)
128.0 ± 13.0
(109-155)
127.9 ± 13.1
(109-160)
T
76.8 ± 9.0
(53-90)
76.7 ± 16.6
(15-93)
76.7 ± 11.9
(15-93)
I
128.4 ± 11.7
(98-149)
133.6 ± 6.1
(123-148)
130.1 ± 10.5
(98-149)
N
82.9 ± 11.7
(59-107)
87.6 ± 11.4
(60-102)
84.5 ± 11.7
(59-107)
Aver.
104.1 ± 7.1
(90-116)
106.5 ± 5.5
(98-115)
104.9 ± 6.7
(90-116)
S: Superior, T: Temporal, I: Inferior, N: Nasal, Aver: Average
There was no difference between sex groups in any parameters. The order of
RNFL was inferior quadrant>superior quadrant>nasal quadrant>temporal quadrant.
DISCUSSION:
This study reported normative values for RNFL thickness in children 6–15 years
of age using Spectralis SD-OCT. Correlations with biometric data showed that RNFL
thickness values were not different in gender groups. Optical coherence tomography,
being non-invasive and fast, is gaining more popularity in evaluating diseases of
childhood including pediatric glaucoma.
There is not enough studies published yet which reports normal values for
children. Only a few studies reported, using Spectralis, normative RNFL datas for
children.14,15 One of them in Turkish children and other one in North American
children. Turk et al reported that the average peripapillary RNFL thickness was 106.45
± 9.41 μm in healthy Turkish children and added that OCT measurements were not
significantly correlated with age, SE, or AL values.14 Yanni et al reported that the
average peripapillary RNFL thickness was 107.6 ± 1.2 μm in healthy American children
and they added that SD-OCT can be used to assess peripapillary RNFL thickness in
children as young as 5 years.
OCT is a powerful technology for the assessment of the RNFL. However,
different OCT devices employ different acquisition technologies and data analysis
software. It has been shown that significant variability in RNFL thickness can exist
among different OCT devices.16 Physician needs to know for normative datas for all
devices and for all patients groups. Using an adult normative database for pediatrics
patents is not agreeable.
CONCLUSION:
This study adds an example of normal reference ranges for RNFL thickness
measured via Spectralis SD-OCT in healthy Middle Eastern children 6–15 years of age.
4
Other races, ethnicities should be studied in future research. Also a possible correlation
of RNFL thickness with axial length, refractive status of the eye, corneal thickness
should be studied.
ACKNOWLEDGEMENTS: The authors declare no conflict of interest.
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